The invention relates to a method for silanol removal from a polymerization solvent in a continuous or consecutive batch wise preparation of a modified conjugated diene/alpha-olefin interpolymer or modified conjugated diene polymer preparation.
Modifying agents for the preparation of modified polymers include those modifiers described in the following references: WO2007047943, JP2003-171418, WO03/029299, WO07/047943, International Application No. PCT/US07/087564, and U.S. Provisional Application No. 61/059278. These references describe the use of modifying agents for the preparation of modified polymers. Modified polymers typically comprise phosphorous-silicon bonds, nitrogen-silicon bonds, or sulfur-silicon bonds. The modified polymers and modifying agents can form silanols upon addition of protolyzing agents, such as organic acids, inorganic acids, and water. In a continuous or consecutive batch process, the silanols are recycled with the polymerization solvent back to the reactor for a consecutive polymerization. There is a need for an effective silanol removal process for such polymerizations.
International Publication No. WO2003093391 A1 (Abstract) discloses phase change materials (PCM) comprising at least one top layer on the surface of the PCM, selected among a layer A and a layer B. Layer A consists of at least one inorganic substance that is selected among an oxide, oxide hydrate, hydroxide and a salt that contains OH groups. Layer B consists of at least one coupling reagent. The reference also relates to production methods for producing surface-modified PCM's of this type and to their use in a supporting medium.
International Publication No. WO2004041398 A2 discloses porous inorganic/organic homogenous copolymeric hybrid material materials, including particulates and monoliths, methods for their manufacture, and uses thereof, for example, as chromatographic separations materials.
U.K. Patent Application 2199817 A discloses a coating solution for forming a SiO2 coating which does not contain halogen ion. The coating solution is obtained by reacting an alkoxysilane and/or an oligomer thereof with water, in the presence of a solid acid catalyst and a solvent.
Japanese Patent Application JP11130864 A (Abstract) discloses a method for producing a composite product of an inorganic-organic hybrid with inorganic particles, capable of efficiently forming chemical bonds on the interfaces of the inorganic-organic hybrids and inorganic particles. The particles are dispersed in a solution containing one or two polysiloxanes and an organoalkoxysiane in an organic solvent.
U.S. Publication No. 200310176559 A1 discloses hydrophobic particulate inorganic oxides useful for reinforcing polymeric composition, for example, rubber. The materials are characterized by the following: (a) the substantial absence of functional groups capable of chemical reaction with rubber; (b) a BET surface area in the range of from 40 to 350 m2/g; (c) a hydroxyl content in the range of 2 to 15 OH/nm2; (d) a carbon content in the range from 0.1 to 6 percent by weight that is substantially non-extractable; (e) a pH in the range from 3 to 10; (f) an M1 Standard White Area less than 0.4 percent, and (g) a methanol wettability from 15 to 45 percent. Compositions such as polymers, cured organic rubber articles, master batches and slurries containing the hydrophobic fillers are also described
Japanese Patent Application JP2007126332 A (Abstract) discloses a water-repellent glass plate, covered with water-repellent, transparent, fine particles covalently bonded to the surface of the plate. A major portion of the surface of each water-repellent, transparent, fine particle is covered with a water-repellent coat. A portion of the water-repellent, transparent, fine particles are covalently bonded to the surface of a base glass plate through an organic film, a part of which contains a reactive functional group at one end, and is covalently bonded to the surface of each transparent, fine particle through Si at the other end. An organic film, which contains a reactive functional group at one end, is covalently bonded to the base glass plate through Si at the other end.
Cost-Effective Surface Modifications of Silica and Alumina Achieved by Way of a Single In-House Set-Up (Abstract), A. Taralp et al., ASC National Meeting, March 2003, discloses surface functionalized porous silica and alumina. Comparison of Octadecyl-Bonded Alumina and Silica for Reverse-Phase High Performance Liquid Chromatography, J. E. Haky et al., J. of Chromatography, 505 (1990), 307-318, discloses chromatographic properties of an octadecyl-bonded alumina (ODA) high performance liquid chromatography (HPLC) stationary phase. The ODA is compared to conventional octadecylsilica (ODS) stationary phases.
Silanol, when present, reacts with alkyl metal initiator compounds, or with living polymer chains in the process of anionic solution polymerization of conjugated dienes, preferably butadiene, or in the process of anionic solution co-polymerization of conjugated dienes with alpha-olefins, preferably of butadiene and styrene. Depending on the silanol concentration, one or more of the following aspects of an anionic polymerization process are deteriorated: (a) the alkyl metal initiator concentration is decreased, and the initiation of the anionic polymerization or copolymerization reaction is negatively influenced, (b) the polymer or copolymer molecular weight characteristics are undesirably altered, (c) the long term production of polymer with consistent polymer characteristics, and thus polymer properties, is hampered, and/or (d) the polymerization reaction is prematurely terminated before achieving the desired monomer conversion. The amount of active initiator compound present in a polymer solution, upon reaction with silanol, is difficult to detect. The use of an additional initiator compound, to correct for initiator lost to reaction with silanol, causes increasing initiator costs. Also the use of an additional initiator compound fraction does not lead to a product qualitatively identical with a product produced without silanol impurity.
Silanols are particularly formed when the modified polymers and modifying agents are exposed to water at a temperature ranging from 90° C. to 150° C. These conditions typically represent those of a steam stripping process, which is the conventional procedure for the isolation of polymer.
Silanols are conventionally removed by using an increased alkyl metal initiator concentration; however this removal process leads to the formation of metal silanolates comprising ionic bonds as shown in Formula 1.

Conventional initiator compounds, such as, for example, C1-C6 alkyl lithium initiators, when contacted with silanols, form compounds comprising ionic bonds as shown in Formula 2.

Compounds comprising Formula 1 or Formula 2 bonds are rendered silanols again, when contacted with water, such as present in conventional polymer isolation processes. Therefore, in case of consecutive batch or continuous polymerization processes, the silanols can accumulate in the polymerization medium over time. Thus at one point, the reduced number of initiator compounds can not be compensated from the economic point of view.
The conventional polymer isolation processes provide no practical way to reduce and/or eliminate silanols in polymer. This issue is particularly a problem for procedures associated with consecutive batch or continuous polymerization processes. Thus, there is a need for a cost effective and efficient process to remove silanols from a polymerization process. This need and others have been met by the following invention.